Photographic emulsion containing optically dye-sensitized silver halide grains of less than 0.2 micron

ABSTRACT

A PHOTOGRAPHIC SILVER HALIDE EMULSION IN WHICH AT LEAST 95% OF THE SILVER HALIDE GRAINS ARE LESS THAN 0.2 MICRON OR IN WHICH THE MEAN GRAIN SIZE OF THE SILVER HALIDE GRAINS IS LESS THAN 0.18 AND WHICH CONTAINS A SENSITIZING DYE HAVING AN OXIDATION POTENTIAL OF LESS THAN 0.90 VOLT IS DISCLOSED.

United States Patent Ofiice Patented Dec. 19, 1972 3,706,566PHOTOGRAPHIC EMULSION CONTAINING OPTICALLY DYE-SENSITIZED SILVER HA-LIDE GRAINS F LESS THAN 0.2 MICRON Keisuke Shiba, Tohru Sueyoshi, AkiraSato, Seiiti Kuhndera, and Motohiko Tsubota, Kanagawa, Japan, assignorsto Fuji Photo Film Co., Ltd., Kanagawa, Japan No Drawing. Filed Feb. 24,1970, Ser. No. 13,774 Claims priority, application Japan, Mar. 7, 1969,44/ 17,261 Int. Cl. G03c 1/08 US. Cl. 96-120 12 Claims ABSTRACT OF THEDISCLOSURE A photographic silver halide emulsion in which at least 95%of the silver halide grains are less than 0.2 micron or in which themean grain size of the silver halide grains is less than 0.18 and whichcontains a sensitizing dye having an oxidation potential of less than0.90 volt is disclosed.

BACKGROUND OF THE INVENTION (1) Field of the invention The presentinvention relates to a photographic silver halide emulsion and moreparticularly to a fine grain silver halide photographic emulsion whichhas been sensitized over the region from the specific absorption wavelength region of the silver halide in the silver halide emulsion to aspectrally sensitized wave length region.

(2) Prior art In the production of photographic light-sensitiveelements, the technique for improving the light sensitivity ofphotographic emulsions is one of the most important techniques andvarious techniques have already been provided. These known techniquesfor improving light sensitivity generally can be divided into those inwhich the light sensitivity is improved during the preparation of thelightsensitive materials and those in which the light sensitivity isimproved during the developing process. The latter technique is,However, accompanied with a tendency toward degradation of thegranularity of silver images of the light-sensitive elements.

The first technique for light-sensitization is further divided generallyinto either chemical sensitization or spectral sensitiztaion (cf., E. K.Mees and T. H. James, The Theory of the Photographic Process, 3rd ed.,par. 12, Mac- Millan Co. (1966).

Chemical sensitization includes such sensitizing methods as reductionsensitization, sulfur sensitization, noble metal sensitization (forexample, salts of gold, platinum, palladium, iridinum or rhodium withthiocyanates), and combinations thereof. But, the application of any ofthese chemical sensitizations increases only the sensitivity of aspecific absorption wave length region of the silver halide. On theother hand, spectral sensitization extends the photosensitive wavelength region from the specific wave length region of absorption ofsilver halide toward the absorption of longer wave lengths.

When a photographic silver halide emulsion containing a sensitizing dyeis subjected to spectral sensitization, the sensitivity of the silverhalide emulsion in the specific absorption wave length region of silverhalide is generally reduced. This phenomenon is called desensitizationby a sensitizing dye. The extent of the desensitization is influencedlargely by the composition of the silver halide emulsion used and thechemical structure of the sensitizing dye.

In cases in which the photographic silver halide emulsion used is notchemically ripened or is a silver iodobromide emulsion having internalsensitivity, the silver halide emulsion is, on the contrary, sensitizedby a socalled desensitizing dye. This phenomenon is well known as theCapri-blue etfect [see, for example, Tamura & Hada, On theDesensitization of Silver Halide Emulsion by Dyes, Journal ofPhotographic Science, II (2), 87 (1967 )1.

However, the sensitivity of a silver halide emulsion obtained using theCapri-blue effect is considerably lower than that obtained by chemicallysensitizing the silver halide emulsion. Thus, in practice this is not avaluable sensitizing method.

In the production of photographic light-sensitive elements, in order toimprove the granularity of silver images, a fine grain silver halideemulsion is required. However, generally, if the grain size of silverhalide is reduced, the light-sensitivity thereof is lowered.

Therefore, it is an important consideration in the production ofphotographic light-sensitive elements to prepare a silver halideemulsion having a silver halide of fine grain size and at the same timehaving a high sensitivity.

It has been found that when a dye having a specific nature is applied toa photographic silver halide emulsion containing silver halide crystalshaving the grain size less than a definite value, the light-sensitivityof the silver halide emulsion in the specific absorption wave lengthregion of silver halide can be increased markedly in spite of that thesilver halide emulsion had been subjected sufliciently to a chemicalripening procedure.

When a dye has an absorption in the wave length region from the blueregion to the red region and the function of spectral sensitization, thesensitivity of a photographic silver halide emulsion can be markedlyincreased over the whole visible wave length regions by the addition ofthe dye to the silver halide emulsion.

Thus, an object of the present invention is to provide a photographicsilver halide emulsion having fine silver halide grains and at the sametime having a high sensitivity over a region from the specificabsorption region of silver halide emulsion in which at least of silverSUMMARY OF THE INVENTION The above-mentioned object of the presentinvention can be achieved by incorporating a dye having an oxidationpotential value of less than 0.9 volt in a photographic silver halideemulsion in which at least 95% of silver halide grains contained in thesilver halide emulsion have grain sizes less than 0.20 micron or inwhich the mean grain size of silver halide grains is less than 0.18micron. By the aforesaid procedure, the sensitivity of the photographicsilver halide emulsion can be uniformly increased over the region fromthe specific absorption wave length region of silver halide to thespectrally sensitized wave length region thereof.

Furthermore, it is particularly preferable in the present invention toincorporate the dye having the above-mentioned properties into aphotographic silver halide emulsion which has been subjected to chemicalripening procedure.

The term oxidation potential used in the present specification, asmeasured by a voltammeter, means the potential at which the dye isoxidized by the anode (cf., P. Delahay, New Instrumental Methods inElectrochemistry, Interscience Publishers (1954), and L. Meites,Polarographic Techniques, 2nd ed., Interscience Publishers (1965).

The oxidation potential described in the present specification is thehalf-way potential of a voltage-current curve obtained by using a rotaryplatinum electrode and a saturated calomel electrode as the electrodesand also using sodium perchlorate as the supporting electrolyte. The dyeis used as an acetonitrile solution having a concentration of from 1Xmole to 1X10 mole [cf., A. Stanienda, Natur Wissenschaften, 47, 353 and512 (1960)].

A series of observed oxidation potentials of dyes may have a deviationof about 100 millivolts by the influence of the contact potentialdifference between liquids, the temperature of measuring the electricresistance of the solution of dye, and the anions of the dyes. However,counter balancing the above-mentioned deviation by using an observedvalue of a dye as the standard (for example, dye I shown below), thereproducibility of the measurement of the oxidation potential can besecured.

As the photographic emulsions employed in the present invention,suitable emulsions are a silver iodobromide emulsion, a silver bromideemulsion, a silver chlorobromide emulsion, and a silveriodobromo-chloride emulsion. More particularly, a silver iodobromideemulsion and a silver bromide emulsion are preferred. The use of asilver chloride emulsion is, however, unprofitable in the presentinvention.

The particular sensitization elfect of the present invention in thespecific absorption wave length region of a silver halide emulsiondepends on the grain size of silver halide particles in the emulsion,even when the halogen atom composition of the photographic emulsion isthe same. Also, the sensitization of the photographic silver halideemulsion of the present invention can be applied to a sensitizing methodsuch as a sulfur sensitization, a reduction sensitization and/or a noblemetal sensitization. Also the sensitization in the present invention canbe applied to a sensitizing method in a developing process. Theparticular sensitization eifect of the present invention in the specificabsorption region of silver halide is more marked as the size of thesilver halide grains in the silver halide emulsion to which the dye isadded is reduced below 0.20 micron. On the contrary, the larger thesilver halide grains, the more the sensitization effect by the presentinvention is reduced. When the size of silver halide grains is 0.25micron or larger, the sensitizing effect by the addition of the dye islost or is converted into a desensitization function usually observed inthe case of using a conventional sensitizing dye. For example, a silveriodobromide emulsion sufiiciently subjected to chemical ripening wasmixed with 1X10 mole/liter of a methanol solution of a thiacarbocyaninein an amount of 8 ml. per 100 g. of the silver halide emulsion and theresultant silver halide emulsion was applied to a support to provide alight-sensitive element, which was subjected to sensitometry using bluelight. When the sensitivity obtained is compared with that Mean grainsize (in microns) 0. 30 sensitizing percent From the results it will beunderstood that the size of silver halide grains used in the emulsion isa very important factor for the specific effect of the presentinvention.

The sensitization effect of the present invention in the specificabsorption wave length region is fundamentally different from theabove-described Capri-blue effect. For example, when phenosafranine isincorporated in a silver iodobromide which was not subjected to achemical ripening or which has a high internal sensitivity, the specificabsorption wave length region of silver halide is sensitized, while thephenosafranine shows only a desensitization effeet to the fine grainsilver iodobromide emulsion employed in the present invention.Similarly, when 5,5',6,6'- tetrachlorobenzimidazolocarbocyanine isincorporated in a silver halide emulsion which shows a Capri-blueefi'ect by the addition of phenosafranine, the silver halide emulsionshows no Capri-blue etfect. On the other hand, when the aforesaidcarbocyanine is incorporated in the fine grain silver iodobromideemulsion containing silver halide grains having the grain size asdefined in the present invention, the additive causes a markedsensitization effect. This fact will be readily understood onconsidering that the oxidation potential of phenosafranine does notsatisfy oxidation potential requirement for the present invention,whereas the oxidation potential of5,5',6,6'-tetrachlorobenzimidazolocarbocyanine is 0.54 volt which is inthe range suited for use in the present invention.

The dyes used in the present invention include merocyanine dyes, cyaninedyes, hemicyanine dyes, rhodacyanine dyes, trinuclear cyanine dyes, andstyryl dyes. Suitable dyes for use have an oxidation potential lowerthan 0.90 volt.

The examples of the dyes used in the present invention are shown belowtogether with the oxidation potentials although the dyes in the presentinvention shall not be limited to them only.

The dyes used in the present invention can be prepared by known methods,that is, can be generally prepared as follows:

The trimethine dye, Dye I, can be prepared by condensing a quaternaryammonium salt represented by the general Formula I and an ortho-formicacid ester in pyridine in the presence of a base such as triethylamine.

Also, the pentamethine dye, Dye H, can be prepared by using in the abovedescribed condensation reaction 1,3,3-triethoxypropene and the likeinstead of the orthoformic acid ester.

Furthermore, the monomethine dye, Dye V, or Comparative Dye C can beprepared by condensing a quaternary ammonium salt intermediate productrepresented by the general Formula II shown below.

-Iqn

it X- (II) and the quaternary ammonium salt represented by the aforesaidgeneral Formula I in a suitable solvent such as an alcohol (e.g.,methanol or ethanol) or pyridine in the presence of a base such astriethylamine.

Also, the benzimidazolocarbocyanine dye, Dye II or IV, can be preparedby condensing a quaternary ammonium salt intermediate productrepresented by the following general Formula III and an ortho-formicacid ester in nitrobenzene in the presence of a base such astriethylamine or condensing the said quaternary ammonium saltintermediate product and a chloral in an alcohol in the presence of analcoholate.

The styryl base dye, Dye XIV or XV, can be prepared by condensing acompound represented by the following general Formula IV -N (IV) and ap-dialkylaminobenzaldehyde in the presence of zinc chloride.

Furthermore, merocyanine dyes, Dye VI, VII, VIII, IX, X, XI or XII,shown above, can be prepared by condensing a ketomethylene compoundrepresented by the following general Formula V and an intermediateproduct represented by the following general Formula VI or VII R X"(VII) 10 in an alcohol (e.g. methanol or ethanol) or pyridine in thepresence of a base such as triethylamine.

In the aforesaid general formulae, Z and Z each represents an atomicgroup necessary to complete a nitrogencontaining heterocyclic ring, suchas a benzothiazole, a naphthothiazole, a benzoselenazole, anaphthoselenazole, a benzoxazole, a naphthoxazole, a quinoline, abenzimidazole, a thiazole, an oxazole, or a terazole ring; Z" representsan atomic group necessary to complete a benzimidazole ring; R, R, and R"each represents an alkyl group such as a methyl group, an ethyl group,or a n-propyl group; a substituted alkyl group such as a fi-hydroxyethylgroup, a fi-carboethoxyethyl group, a carboxymethyl group, afl-carboxyethyl group, a ,B-sulfoethyl group, a 'y-sulfopropyl group, afi-sulfobutyl group, a B-phenylethyl group, or an allyl group (orvinylmethyl group); or an aryl group; L represents a methine chain or amethine chain substituted by an alkyl group such as a methyl group, anethyl group, and the like; X represents an anion; Q represents an atomicgroup necessary to complete a ketomethylene ring, such as a rhodaninenucleus, a hydantoin nucleus, 21 thiohydantoin nucleus, an oxazolidinonenucleus, or a pyrazolone nucleus; and n is 0, 1 or 2.

The above-mentioned dyes in the present invention can be used togetherwith other additives such as stabilizers, antifoggants, sensitizingdyes, hardening agents, wetting agents, water-soluble high molecularweight compounds, e.g., gelatin or gelatin derivatives, film-denaturingagents, and couplers if desired. Also, it is especially suitable thatthe dye in the present invention be used as a dye having theabove-mentioned specific sensitizing effect and a spectral sensitizationfunction.

The photographic silver halide emulsion of the present invention can beapplied to any suitable support such as a glass plate, a triacetylcellulose film, a polyethylene terephthalate film, other plastic films,a plastic sheet, a baryta-coated paper, a resin-laminated paper, and thelike.

The invention will be more practically described by referring to thefollowing examples.

EXAMPLE 1 A silver iodobromide emulsion was prepared in a conventionalmanner and was subjected to physical ripening or chemical ripening inthe conventional manner. The silver halide emulsion contained 1 molepercent of iodide ion and the mean size of the silver halide grains inthe emulsion was 0.06 micron. Fifty grams (50 g.) of the silver halideemulsion was placed in a beaker and melted by heating the beaker in abath at 40 C. A specific amount of a solution of the dye of the presentinvention having a concentration of 1X10" mole/liter was added to themolten emulsion with stirring and 7 ml. of the resultant emulsion wasapplied to a glass plate of cabinet size and dried.

The light-sensitive plate was exposed by optical wedge to a tungstenlight of a color temperature of 2854 K. by means of a S-typesensitometer made by Fuji Photo Film Co., through a blue filter No. K-31or a yellow filter No. K-12. Subsequently, the photographic plate wasdeveloped for 10 minutes at 20 C. in a developer having the followingcomposition, and then fixed.

Developer composition:

The optical density of the photographic plate thus treated was measuredby using a S-type sensitometer made 1 1 by Fuji Photo Film Co. and theresults of the relative blue filter sensitivity, Sb, and the relativeyellow filter sensitivity, Sy, at the point where the optical densitywas fog+0.2 are shown in the following table.

Oxidation Addition potential amount No. Dye (volt) (ml.) Sy Sy 1 None100 I 0. 77 2 252 1, 660 I 0. 77 4 380 2, 890

3 III 0.54 2 800 10,000 III 0. 54 4 630 10, 000

4. 1V 0. 48 2 316 3, 630 IV 0.48 4 562 5,000

6 VI 0. 77 2 136 34 VI 0.77 4 141 50 7 VII 0.72 2 250 660 VII 0. 72 4250 1, 150

8 VIII 0.52 2 240 635 VIII 0. 52 4 330 1, 000

9 IX 0.45 2 240 790 IX 0.45 4 400 1, 590

10 X 0.42 2 1, 180 2,340 X o. 42 4 1, 180 3, 160

11 XI 0.33 2 562 2,520 XI 0.33 4 562 2,350

12-, XII 0.82 2 136 100 XII 0. 82 4 115 141 13 XIII 0.35 2 330 12, 600XIII 0.35 4 330 14, 100

14 XIV 0.68 2 895 562 XIV 0. 68 4 1, 180 800 15 XV 0.61 2 167 50 XV 0.614 200 100 16 XVI 0.67 2 142 50 XVI 0.67 4 142 70 Control A 1. 01 2 100 A1.01 4 100 Control... B 1. 18 1 31 B 1. 18 2 10 EXAMPLE 2 The sameprocedure as used in Example 1 was followed using a silver chlorobromideemulsion. The bromine content in the silver halide emulsion used was 40mole percent and the mean size of the silver halide grains in theemulsion was about 0.1 micron. The results are as follows.

.What is claimed is:

1. In a photographic negative silver halide emulsion containing a silverhalide, excluding silver chloride, and a sensitizing dye, theimprovement which comprises at least 95% of the silver halide having agrain size less than 0.2 micron, said dye having an oxidation potentialof less than 0.90 volt and being a member selected from the groupconsisting of a merocyanine dye, a cyanine dye, a hemicyanine dye, arhodacyanine dye, a trinuclear cyanine dye, and styryl dye.

2. In a photographic negative silver halide emulsion containing a silverhalide, excluding silver chloride, and a sensitizing dye, theimprovement which comprises the silver halide having a mean grain sizeless than 0.18 micron, said dye having an oxidation potential of lessthan 0.90 volt, and being a member selected from the group consisting ofa merocyanine dye, a cyanine dye, a hemicyanine dye, a rhodacyanine dye,a trinuclear cyanine dye and a styryl dye.

3. The photographic negative silver halide emulsion as claimed in claim1, wherein said dye is a member selected from the group consisting of:

4. The photographic negative silver halide emulsion as claimed in claim2, wherein said dye is a member selected from the group consisting of:

N C=CHCH s H O\ C 3 0 (I /C==CHCH =s 02H: N 0

and

5. The photographic negative silver halide emulsion as claimed in claim1, wherein said emulsion has been subjected to chemical ripening.

6. The photographic negative silverhalide emulsion as claimed in claim1, whereinsaid silver halide is silver iodobromide, silver bromide,silver chlorobromide or silver iodobromo-chloride.

7. In a photographic negative light-sensitive element comprising asupport and one or' more photographic silver halide emulsion layerscoated thereon, the improvement which comprises at least one of thelayers containing a photographic silver halide emulsion as claimed inclaim 1. a

8. In a photographic light-sensitive element comprising a support andoneprzmore photographic @silver halide emulsion layers; coated thereon,the improvement which comprises at least one of the layers'ac'ontaininga photographic silver halide emulsion as claimed in claim 5.

9. The photographic negative silver halide emulsion as claimed in claim2, wherein said emulsion has been subjected to chemical ripening.

10. The photographic negative silver halide emulsion as claimed in claim2, wherein said silver halide is silver iodobromide, silver bromide,silver chlo'ro-bromide or silver iodobromo-chlorid'e' 11. In aphotographic negative light-sensitive element comprising a support andone or more photographic silver halide emulsion layers coated thereon,,-.the improvement which comprises at least one of the layers containinga photographic silver halide emulsion as claimed in claim 2.

12. In a photographic light-sensitive element comprising a support andone or more photographic silver halide emulsion layers coated thereon,the improvement which comprises at least one of the layers containing aphotographic silver halide emulsion as claimedin claim 9.

References Cited UNITED STATES PATENTS J. TRAVIS BROWN, Primary ExaminerW. H. LOUIE, JR., Assistant Examiner US. 01. X.R.

j UNITED STATES PATENT OFFICE- CERTIFICATE OF CORRECTION Patent No. 3,706, 566 Dated December 19, 1972 Keisuke Shiba ei: a1 Inventor(s) It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

In The Specif icefcion;

Column 2 1 line '14, delete "emulsion in which at least 95% of silver"and insert to the spectral sensitizing region.--

Signed and sealed this 24th day of December 1974.

Attest:

McCOY M. GIBSON JR. 7 C. MARSHALL DANN Attesting Officer Commissioner ofPatents USCOMM-DC 60376-P69 u.s GOVERNMENT PRINTING OFFICE 8 93 o F ORMPO-105O (10-69)

